This invention relates to an overhead or ceiling heater panel for room heating mainly with radiant heat. Overhead heaters of the kind concerned comprise one or more relatively elongate radiation plates in the form of an extruded aluminum profile, a reflector mounted with a spacing behind the radiant plate as seen in relation to the heat radiation direction, and attached to the radiant plate at the two longitudinal edges thereof, as well as a surrounding box-like housing mainly composed of sheet members, for each overhead heater. Each fitting, i.e. each box-like housing may be provided with one, two, three or possibly more, radiant plates. These radiant plates may, moreover, in certain designs be adapted for angular adjustment so as to direct the heat radiation towards desired places in the room to be heated.
An electrical overhead heater with an elongate, boxshaped fitting for delivering radiant heat and designed as a ceiling or overhead heating panel is described for example in Norwegian Patent No. 142 851. Moreover, it may be mentioned that ceiling heaters of the type concerned are manufactured and sold under the trademark "ELZTRIP" (registered trademark).
Two important considerations in connection with a product as discussed here, are that it must be economical in production and operation as well as very robust so that these ceiling heaters may be employed in the most different environments, particularly in industry and workshop premises, without problems.
It has now been found that under these circumstances the extruded aluminum profile which constitute the above radiant plate, may be subject to some deformation, in particular skew after some time of operation. The explanation thereof is believed to be that the radiant plate together with the reflector which is mounted thereon, by repeated heating and cooling in use, will have an accumulated mutual displacement or induced force, which contributes to the skew observed. Possibly another or supplementary explanation may be that material strains in the extruded aluminum profile give rise to the deformations. Such deformation or skew may be further accentuated by the fact that the high temperatures occurring under operation, i.e. temperatures for example in the range 300.degree.-350.degree. C., to some degree make the aluminum material softer so that the mechanical strength and rigidity are not as high as at room temperature.